This invention relates to marine seismic detector arrays and more particularly to a replacement bulkhead for a marine seismic cable or streamer section.
A seismic cable may comprise one or more interconnected sections, each section including a flexible tube made, e.g. of plastics material, such as polyurethane or polyvinyl chloride, several inches in diameter and about one hundred to three hundred feet long, the tube having a wall thickness of about one-sixteenth of an inch. The tube houses hydrophones, depth transducers and other electrical components distributed along the length of the tube. Three steel lines inside the tube and extending the length thereof take tension load on the cable. At intervals of one or two feet along the length of the tube, bulkheads divide the cable section into compartments, within each of which is a group of electrical components. Electrical conductors connecting the electrical components with the end of the cable or with each other extend through a single center opening in each bulkhead. The three tension lines extend through three off-axial holes in the bulkhead, the holes being positioned with their centers 120 degrees apart around the circumference of the bulkhead. The remaining volume inside the tube is filled with oil to give the cable the desired positive, negative, or neutral buoyancy.
The bulkheads have cylindrical outer peripheries and fit closely within the tube, holding the tube open and cylindrical rather than allowing it to flatten out.
For a description of method and apparatus for assembling a seismic cable, see U.S. Pat. No. 3,885,286--Hill.
The bulkheads not only hold the tube in shape, but also keep the tension lines from becoming tangled, and provide buffers, to a certain extent protecting the electrical components from being impacted, e.g. when a seismic cable or streamer composed of perhaps several thousand feet of cable sections is wound up on a reel. The bulkheads are therefore also referred to as streamer spacers.
A repair problem arises when one of the bulkheads in a streamer section is cracked, broken or otherwise damaged, e.g. when the streamer is being wound on a reel. It is necessary to remove the tube, remove the broken spacer, and then in order to install a new spacer the electrical conductors and tension lines must be cut to enable them to be threaded through the new spacer. Since there are as many as 520 electrical conductors in a streamer section, the cost of such a repair, requiring splicing of electrical conductors, is almost prohibitive.
It is an object of the invention to solve the problem of repairing a streamer section having a damaged bulkhead.